| Notes:
1) The Mark XXIII designation was apparently
given to both the quadruple (four-gun) turrets originally planned for the
Edinburgh class and to the triple (three-gun) turrets actually used on
the Edinburgh and Fiji classes. See Note 5.
2) The Mark XXII and Mark XXIII Triple
Mounts had the center gun set back 30 inches (76.2 cm) in order to reduce
the interference between shells in flight, give the loading crews more
"elbow room" and to better balance the revolving mass. Triple mounts
had two right-handed guns and one left-handed gun.
3) The weight differences for the triple
mounts is primarily due to armor thickness. For the Mark XXII, Southampton
had 1 inch (2.54 cm) armor all around. Gloucester had 3.9 inch (10
cm) glacis plate armor with the rest 2 in (5.1 cm). For the Mark
XXIII, Edinburgh had 3.9 inch (10 cm) glacis plate and the rest 2 in (5.1
cm). Fiji had 2 inch (5.1 cm) glacis plate and roof, the rest was
1 inch (2.54 cm).
4) Each mounting had two training engines.
When both were used together, train rate was 5 degrees per second, but
using just one engine sped the training up to 7 degrees per second.
5) The Edinburgh class were originally
planned to carry four quadruple mountings. Tests at Shoeburyness
in early 1936 with a mockup where all four guns were equally spaced at
42 inches (106.7 cm) apart showed considerable shell interference and collision
problems, with the resultant large dispersal patterns. A later design
had the guns mounted as two pairs, somewhat similar in concept to the French
quad mounts. This design had each pair of guns only 27.5 inches
(69.9 cm) apart and the innermost pair 46.5 inches (118.1 cm) apart.
This design did not produce acceptable results and the quad mounting was
cancelled in favor of an improved triple mounting. Delay coils were
under consideration at the time of the cancellation.
6) Many cruisers had "X" turret removed
as weight compensation for added electronic equipment. Its place
was usually taken by additional AA guns. HMS Belfast, of the larger
"Modified Town" class, was unique in keeping all four of her mountings
throughout the war and beyond.
7) The gunlayers usually followed the pointer
using hand control, changing to power elevation only for larger movements.
8) Guns were hand loaded and rammed.
9) The twin Mark XXI was a "short trunk"
design powered by a 65 HP electric motor and hydraulic pump using light
mineral oil, located on the revolving structure. The guns were individually
sleeved and runout was via compressed air. Elevation was by a swashplate
engine driving a worm gear. There were two training engines which
were usually operated together as control was better, although training
speed was faster when only one was used. Provisions were made to
allow manual training. The fore and aft turret groups had a single
magazine, with each turret having its own handling room, which was part
of the fixed structure. Charges were passed by hand from the magazine
through a revolving flashtight scuttle to the cordite handling room.
From here, charges were delivered by a single endless chain hoist to each
handling room at the rate of 16 per minute for A, B and X mountings.
For Y mounting, the handling room was directly above the magazines and
the hoist was replaced by two hand ups. Shells were delivered to
the handling room by another endless chain hoist at the rate of 16 shells
per minute. From the handling room, another endless chain for each
gun carried the powder charge to the rear of the gun. Shells were
delivered vertically to the gunhouse, where a tilting bucket transferred
them to a fixed tray. From here they went to an intermediate tray
and then to the loading tray which pivoted on an arm from the cradle.
Shells were hand rammed and then charges were placed on the loading tray
and hand loaded.
10) The triple Mark XXII was a short trunk
design with similar features as the Mark XXI. The electric motor
was increased to 103 HP. These ships had a magazine for each turret
with a shell room on the same level. A handling room just below the
turret was part of the fixed structure. Dual electric powered endless
chains delivered 32 charges per minute from the magazine to the handling
room. Charges were carried by hand to crewmen in "cordite pockets"
attached to the revolving structure where they were passed by hand via
hand-ups into the gunhouse. Shells were delivered by dual hoists
to the handling room at the rate of 32 rounds per minute. Each gun
had its own shell hoist attached to the revolving structure that delivered
shells vertically to the gunhouse. Arrangements were similar to those
for the twin mounts, with the exception that the center gun had a longer
intermediate tray as it was further from the hoist than the other two guns.
11) The triple Mark XXIII was powered by
a 114 HP motor and had a completely different ammunition supply systems
as compared to the earlier Marks. These were "long trunk" designs
with each turret having a magazine and a handling room with a shell room
located one deck above. Charges were passed via scuttles from the
magazines to a handling room where they were loaded onto endless chain
hoists. There was one charge hoist per gun and these ran directly
from the handling room up to the gunhouse, with the charges being delivered
vertically. Each hoist could deliver 10 (Wingate) or 12 (Campbell)
charges per minute. In the shell room, shells were passed to an electrically
powered and independently-revolving shell ring that could hold up to 56
projectiles stowed inclined with noses upwards and outwards. From
here they were passed by hand to the loading trays of the shell hoists.
Each gun was provided with its own shell hoist which could supply 10 (Wingate)
or 12 (Campbell) shells per minute and which delivered the shells vertically
to the gunhouse (both Wingate and Cambell agree that the maximum rate of
fire was 8 rounds per minute regardless of which is correct about the rate
of ammunition supply). Arrangements for moving projectiles to the
breeches were similar to those for the Mark XXII. There was also
an auxiliary cordite supply to the rear and left of the center shell hoists
and an auxiliary shell hoist on the right hand side to the rear of the
right hand shell hoist. Cordite containers were disposed of by pushing
them into chutes at the rear of the gunhouse. Each turret had a crew
of 46 men as follows: Captain of Turret (CT), Local Sight Layer (LSL),
Turret Trainer (TT), Sightsetter (SS), Telephone Operator (TO), Three Gun
Crews (7 men each), Shell Room Crew (9 men), Cordite Handling Room Crew
(3 men) and Magazine Crew (8 men). In addition, each pair of turrets
was allotted one Ordnance Artificer (OA) and two Electrical Mechanicians
(EM).
12) Gun axes were 84 in (213 cm) apart
on the Mark XXI mounting and 78 in (198 cm) apart on the Mark XXII and
Mark XXIII mountings.
13) As these guns were hand-rammed, firing
at high elevations meant that the guns needed considerable time to depress
to the loading elevation and then elevate back up into firing position.
14) The Mark XXIV was a war-time development
based upon the Mark XXII. This was to have achieved a dual-purpose
capability by increasing the maximum elevation to +60 degrees and possibly
using a new, fully-automatic 6 inch (15.2 cm) gun. However, the barbette
and roller path diameters were no larger than the previous triple mountings,
which would have entailed a rather cramped design. This project was
superseded by the Mark XXV which was in
turned cancelled by the end of the war. |
